On many conventional gasification systems there has been difficulty in fuel delivery and ash removal from the gasifier primary chambers. This has been especially apparent on high ash fuels as well as fuels with low ash melting or fusion temperatures.
It has been recognized that many industrial and agricultural solid organic by-products, such as wood chips, agricultural waste, and other biomass material, contain large amounts of chemical energy. The substantial increases in the cost of traditional fuels, such as natural gas, have provided substantial economic incentive to try to develop effective and efficient techniques for recovering the energy in these organic by-products, energy that traditionally was not recovered to any substantial extent. Such organic materials, which are frequently referred to as “biomass” materials, are now successfully utilized to some extent as fuel in some very large industrial systems, for example, in firing the recovery boiler in a pulp or paper mill. However, the higher capital cost which has heretofore been associated with biomass energy recovery systems has precluded their successful use in small or even medium size energy recovery systems. Energy recovery systems, of the size from about 500,000 to 40,000,000 BTU/Hr., are used in schools, nursing homes, and small industrial and commercial establishments. Among the U.S. patents that have been issued on inventions relating to the recovery of energy from wood chips or similar organic materials are U.S. Pat. No. 4,184,436, to Palm, et al.; U.S. Pat. No. 4,312,278, to Smith, et al.; U.S. Pat. No. 4,366,802, to Goodine; U.S. Pat. No. 4,321,877, to Schmidt, et al.; and U.S. Pat. No. 4,430,948, to Ekenberg. However, it is not known that any of the inventions described in these patents have been successfully adapted to recovering biomass energy on a cost-effective basis in small and medium size energy recovery system. Dealing with high ash fuels has proved especially difficult for many of these processes.